Anti-corrosive pigments and method for making the same

ABSTRACT

The invention relates to a paint and/or a coating composition including anti-corrosive pigment comprises a metal salt comprising a metal cation and an anion and a metal oxide or a metal hydroxide where the molar ratio of the total metal to the anion is in the range of 1:4 to 1:120.

FIELD OF TEE INVENTION

[0001] The present invention relates to compositions of anti-corrosivepigments and to a method for making the same. More specifically, thepresent invention relates to heavy metal free anti-corrosive pigmentsand to a method for making the same.

BACKGROUND OF THE INVENTION

[0002] Anti-corrosive pigments are used to protect metal surfacesagainst oxidation and corrosion. Those pigments usually include heavymetals salts, which hinder the rusting of the metal surface by eithercathodic or anodic inhibition mechanisms. Upon dissolving in the aqueousphase, commercial available anti-corrosive pigments partially dissolvedto provide hydrated metal cation and hydrated anion solutions, whichreacts with the metallic surface. The reaction between the partiallysolubilized pigments provides the desired inhibition of corrosion.

[0003] Zinc compounds such as zinc phosphate and zinc chromate arecurrently widely used as anti-corrosive pigments. Zinc is a heavy metalelement and is considered to be toxic at certain concentrations.

[0004] Magnesium phosphate salts, and especially tri-basic magnesiumphosphate were presented as possible anti-corrosive pigments. U.S. Pat.No. 3,960,611 to Walker discloses a composition for anti-corrosivepigments containing magnesium phosphate. This composition was found toprovide only a moderate corrosion inhibition.

[0005] The anti-corrosivity of magnesium phosphates was significantlyimproved by applying molten magnesium salt on the surface of ferricmaterials.

[0006] U.S. Pat. No. 4,411,876 to Sherif, discloses an anti corrosivepigment comprising tri-magnesium phosphate salts. The production oftri-magnesium phosphate salts includes admixing of mono-magnesiumphosphate solution with a slurry of magnesium hydroxide in pH below 6.8.

[0007] However, it is acknowledged that maintaining of pH higher 9.0 isprofitable for corrosion inhibition. A composition that provides for abuffering effect in a basic range is thus preferred.

[0008] U.S. Pat. No. 6,331,202 to Applicant discloses anti-corrosiveamino-based compositions, including both oxyaminophophate and oneselected from oxynitrite, oxymetalphosphate, oxyborate or oxysilicate.

[0009] Similarly, U.S. Pat. No. 6,3312,812 to Hauser et al. disclosesanti-corrosive compositions including both transition elements such asmetals, and amine-containing materials.

[0010] The object of the invention is to provide a non-toxicanti-corrosive pigment that does not contain heavy metals and performequally or better then commercial available anti-corrosive pigments.

SUMMARY OF THE INVENTION

[0011] The invention relates to an anti-corrosive pigment comprising ametal salt comprising a metal cation and an anion and a metal having atleast one oxygen atom where the molar ratio of the total metal to theanion is in the range of 1:4 to 1:120.

[0012] The invention also relates to an anti-corrosive pigment where themetal is magnesium, calcium or iron, or any combination thereof.

[0013] The invention also relates to an anti-corrosive pigment where themetal having at least one oxygen atom is magnesium having at least oneoxygen atom selected from magnesium oxide, magnesium hydroxide or anycombination thereof.

[0014] The invention also relates to an anti-corrosive pigment where themetal having at least one oxygen atom comprising iron such as ferrousoxide, ferrous silicate, a slag material, an iron containing industrialeffluent, or any combination thereof.

[0015] The invention also relates to an anti-corrosive pigment where themetal having at least one oxygen atom comprising calcium such as calciumoxide, calcium hydroxide, calcium bicarbonate, calcium carbonate, or anycombination thereof.

[0016] The invention also relates to an anti-corrosive pigment where themetal salt is a phosphate salt such as magnesium phosphate.

[0017] The invention also relates to an anti-corrosive pigment furthercomprising a pH buffering agent, for example, as amine-containingsubstance such as monoethyl amine, diethyl amine, triethyl amine,monoethanol amine, diethanol amine, triethanol amine, 1,2-diazide,1,2,3-triazide, dicyclohexylamine, aliphatic amines, aromatic amines,melamine hexamethylentetiamine and pentaethylenetetramine, ammoniumhydroxide, amino acid, and poly amines.

[0018] The invention also relates to an anti-corrosive pigment furthercomprising a pH buffering agent, for example, a base such as potassiumhydroxide, sodium hydroxide, calcium hydroxide.

[0019] The invention also relates to an anti-corrosive pigment havingfinal pH of about 7 to 11, and having solubility in equilibrated waterwhich is greater than about 0.2%.

[0020] The invention also relates to an anti-corrosive pigment whereinthe metal having at least one oxygen atom comprises magnesium compoundin combination wit a calcium compound wherein the magnesium compound isfor example, magnesium oxide, magnesium hydroxide or any combinationthereof, and wherein the calcium compound is, for example, calciumoxide, calcium hydroxide or any combination thereof.

[0021] The invention also relates to an anti-corrosive pigment whereinthe metal having at least one oxygen atom comprises magnesium compoundin combination with a iron compound wherein the magnesium compound ismagnesium oxide, magnesium hydroxide or any combination thereof, andwherein the iron compound is iron oxide, iron hydroxide or anycombination thereof.

[0022] The invention also relates to an anti-corosive pigment furthercomprising a preservative in a range of 0.1 to 10% (w/w) of the pigmentweight, such as, biocides, fungicides, algaecides, sporocides,insecticides, herbicides, citrimide, chlorohexadine and the like, andquaternary amines, such as Querton KKBCL-50 or Querton 246, QuertonGCL-50, Querton 210CI50, or Querton GCL-50, boric acid, sodium borate,zinc oxide or cupper oxide.

[0023] The invention also relates to an anti-corrosive pigment furthercomprising a surface-active agent in the range of 0.2 to 2% (w/w) of thepigment weight, such as, lingosuiphonates or oleic acids.

[0024] The invention also relates to an anti-corrosive pigment furthercomprising a coloring agent in the range of 0.1 to 40% (w/w) of thepigment weight, such as, fuchsin, rohdamine, methylene blue, iron oxide,methyl violet, or alizarine.

[0025] The invention also relates to an anti-corrosive pigment furthercomprising a UV stabilizer, a UV absorber, and a UV enhancer.

[0026] The invention also relates to an anti-corrosive pigment whereinthe pigment of in a waterborne material selected from paint, coating,plaster or filler wherein said pigment is in the range of 1.7 to 25%(w/w) of the waterborne material.

[0027] The invention also relates to an anti-corrosive pigment whereinthe pigment of in a solvent base material selected from paint, coating,plaster or filler wherein the pigment is in the range of 1.7 to 25%(w/w) of the solvent base material.

[0028] The invention also relates to an anti-corrosive pigment whereinthe pigment of in an emulsion wherein said pigment is in the range of1.7 to 25% (w/w) of the emulsion.

[0029] The invention also relates to a method for the production of ananti-corrosive pigment, the pigment comprising a) a metal saltcomprising a metal cation and an anion, and b) a metal having at leastone oxygen atom; the method comprising the step of mixing an acid of theanion with the metal having at least one oxygen atom, thereby generatingthe metal salt; wherein the molar ratio of the total metal to the anionis in the range of 1:4 to 1:120.

[0030] The invention also relates to a method for the production of ananti-corrosive pigment, wherein the acid is phosphoric acid and themetal having at least one oxygen atom is magnesium oxide or magnesiumhydroxide and wherein the acid is diluted by water to obtain a 5-15%(wt) solution and the metal having at least one oxygen atom is graduallyadded to a range of 7-35% (wt) of the pigment.

[0031] The invention also relates to a method for the production of ananti-corrosive pigment, wherein additional magnesium phosphate salt isgradually admix to the phosphoric acid and metal having at least oneoxygen atom to yield a molar ratio of the total magnesium to thephosphate in the range of 1:4 to 1:120.

[0032] The invention also relates to a method for the production of ananti-corrosive pigment, comprising the step of admixing 5 to 15% (wt)phosphoric acid with 7 to 35% (wt) magnesium oxide or magnesiumhydroxide so as to obtain pH of about 7 to 11 in the anti corrosivepigment.

[0033] The invention also relates to a method for the production of ananti-corrosive pigment, comprising the step of gradually admixing 7 to35% (wt) magnesium oxide or magnesium hydroxide to 5-15% (wt) phosphoricacid solution so as to achieve solubility of the pigmentmagnesium-containing ingredients which is higher than 0.2%.

[0034] The invention also relates to a method for the production of ananti-corrosive pigment, comprising the step of gradually admixing 7 to35% (wt) magnesium oxide or magnesium hydroxide to 5-15% (wt) phosphoricacid solution so as to achieve solubility of the pigmentmagnesium-containing ingredients which is approximately in the range0.2%-0.8%.

[0035] The invention also relates to a method for the production of ananti-corrosive pigment, comprising the step of gradually admixing 5-15%(wt) phosphoric acid solution, 3-10% (wt) of at least one aminecontaining substance and 7 to 35% (wt) magnesium oxide or magnesiumhydroxide in water.

[0036] The invention also relates to a method for the production of ananti-corrosive pigment, comprising the steps of admixing 3-10% (wt) ofat least one amine containing substance or base in water; admixingphosphoric acid to the amine containing solution or base so as 5-15%(wt) of amino phosphoric acid solution is obtained.

BRIEF DESCRIPTION OF THE FIGURES

[0037] The present invention will be understood and appreciated morefully from the following detailed description taken in conjunction withthe drawings in which:

[0038]FIG. 1 presents the molar ratio of Mg⁺²/phosphate as a function ofthe number of equilibrating steps of a tri-magnesium diphosphateoctahydrate product. The small graph presents a fine scale of the abovegraph.

[0039]FIG. 2 presents the Mg⁺²/phosphate molar ratio as a function ofthe number of equilibrating steps of magnesium phosphate salt in accessof 50% magnesium oxide.

[0040]FIG. 3 presents the Mg⁺²/phosphate molar ratio as a function ofthe number of equilibrating steps of magnesium phosphate salt in accessof 50% magnesium oxide and with addition of a pH-buffering agent.

DETAILED DESCRIPTION OF THE INVENTION

[0041] In the following description, various aspects of the inventionwill be described. For purposes of explanation, specific configurationsand details are set forth in order to provide a thorough understandingof the present invention. However, it will also be apparent to oneskilled in the art that the present invention may be practiced withoutthe specific details presented herein. Furthermore, well known featuresmay be omitted or simplified in order not to obscure the presentinvention.

[0042] Embodiments of the invention relate to a heavy metal freeanti-corrosive pigment and a method for producing such anti-corrosivepigment, for inhibiting corrosion of metallic surfaces. Corrosion isdefined herein as a process that seeks to reduce the binding energy inmetals and to all practical appearances of said process. Metallic ormetal is defined herein as any substance able to be subjected tocorrosion including, for example, magnesium and calcium. Molar ratiodefined herein as the ratio between total metal to anion of the pigment.This ratio is measured by dissolving to equilibrium 10 grams of thedried pigment in 100 ml distilled water at 25° C. and than measuring thequantities of the total metal and anion in the water. Total metal meansthe total metal in the pigment, i.e., the metal in the salt and in theoxide. The pH of the pigment is measured by suspending 10 gram ofpigment in 100 ml distilled water and measures the pH of the suspension.

[0043] In some embodiment of the invention an anti corrosive pigment isproduced. The anti corrosive pigment includes a composition of metalhaving at least one oxygen atom such as metal oxide or metal hydroxideand metal salt where the composition is at least partially soluble in aliquid phase. The metal having at least one oxygen atom includes atleast one metal cation and one oxygen or hydroxyl, respectively. Themetal salt includes at least one metal cation and at least one anion.The molar ratio of the total metal to the anion is in the range of 1:4to 1:120.

[0044] In some embodiment the concentration of the metal cation ishigher the concentration of the metal anions.

[0045] In some embodiment, the metal may be, for example, magnesium,calcium iron, etc. In another embodiment the metal may be a combinationof at least two kinds of metal such as magnesium and calcium, magnesiumand iron, iron and calcium, etc. In one embodiment the metal salt maybe, for example, a phosphate salt such as magnesium phosphate salt.

[0046] In some embodiment the metal having at least one oxygen atom maybe magnesium compound, for example, magnesia, magnesium hydroxide,magnesium oxide, etc. In another embodiment the metal having at leastone oxygen atom may be, for example, calcium oxide, calcium hydroxide,calcium carbonate, calcium bicarbonate, etc. In another embodiment themetal having at least one oxygen atom may be iron oxide compound, forexample, ferrous oxide, ferrous silicate, a slag material, an ironcontaining effluent, etc.

[0047] In some embodiment the metal having at least one oxygen atomincludes magnesium oxide or magnesium hydroxide compound in combinationwith an calcium oxide or calcium hydroxide compound.

[0048] In some embodiment the metal having at least one oxygen atomincludes magnesium oxide or magnesium hydroxide compound in combinationwith an iron oxide or iron hydroxide compound.

[0049] In some embodiment the pigment may further include pH-bufferingagents for increasing the pH of the obtained pigment to above pH 7. ThepH buffering agent may be an amine-containing substance. Theamine-containing substance may be, for example, monoethyl amine, diethylamine, triethyl amine, monoethanol amine, diethanol amine, triethanolamine, 1,2-diazide, 1,2,3-triazide, dicyclohexylamine, aliphatic amines,aromatic amines, melamine, hexamethylentetramine andpentaethylenetetramine, ammonium hydroxide, amino acids, poly amines,etc. A base may substitute the amine-containing substance. The base maybe, for example, potassium hydroxide, sodium hydroxide, calciumhydroxide, etc.

[0050] In some embodiment, the final pH of the anti-corrosive pigment isin the range of about 7 to 11. In some embodiment, the pH of theanti-corrosive pigment is approximately 7. In some embodiment, the pH ofthe anti-corrosive pigment is approximately 9.

[0051] In some embodiment, the solubility of the magnesium components ofthe pigment composition is greater than 0.2%, when measured inequilibrated water. In another embodiment, the solubility of themagnesium components of the pigment composition is between 0.2%-1.0%. Inanother embodiment, the solubility of the magnesium components of thepigment composition is between 0.2%-0.8%. In another embodiment, thesolubility of the magnesium components of the pigment composition isbetween 0.2%-0.5%.

[0052] In some embodiment of the invention, the anti-corrosive pigmentmay include at least one preservative in a range of 0.1 to 10% (w/w) ofthe pigment weight. The preservative may be for example, biocides,fungicides, algaecides, sporocides, insecticides, herbicides etc.

[0053] According to another embodiment of the invention the anticorrosive pigment may include at least one preservative such as, forexample, citrimide, chlorohexadine and the like, and quaternary amines,such as Querton KKBCL-50 or Querton 246 (namely benzalkonium chloride),Querton GCL-50, Querton 210CI50, or Querton GCL-50 (i.e., quaternaryamine comprising aliphatic and/or amine residues), etc.

[0054] According to another embodiment of the invention the anticorrosive pigment may include at least one inorganic preservative suchas, for example, boric acid, sodium borate or any other suitable borate,zinc oxide or cupper oxide, etc.

[0055] According to some embodiment of the invention surface-activeagents may be incorporated in either the anti-corrosive pigment or inthe waterborne, emulsion or solvent-base material comprising thepigment. The active agent is in the range of 0.2 to 2.0%(w/w) of theweight of the pigment. The surface-active agents, optionally pretreatedwith nitrogen-containing materials, may be utilized for homogenizationof the reaction mixture. The surface active agents may be, for example,lingosulphonates and the like, oleic acid and the like, etc.

[0056] According to one embodiment of the invention the anti-corrosivepigment may additionally include, or incorporated with, any suitablecoloring agents such as, for example, fuchsin, rohdamine, methyleneblue, iron oxide, methyl violet, alizarine, etc. The coloring agent isin the range of 0.1 to 40% (w/w) of the pigment weight. Additionally,the anti corrosive pigment may include, for example, UV stabilizer, UVadsorber, UV enhancer, etc.

[0057] It is appreciated that the composition according to the presentinvention may be incorporated, introduced or dispersed in any suitablewaterborne, emulsion, or solvent-base material such as, for example,paint, coating, plaster or filler. According to an embodiment of theinvention, the waterborne or solvent-base material may be, for example,acryl, alkyd, epoxy, polyester, polyurethane, or chlorinated rubber. Theconcentration of the anti corrosive pigment in the waterborne, emulsion,or solvent-base material may be in the range of 1.7 to 25% (w/w).

[0058] According to some embodiments of the present invention, a methodfor producing anti-corrosive pigment including a) a metal saltcomprising a metal cation and an anion, and b) a metal oxide and/or ametal hydroxide is introduces. The method includes a step of mixing anacid of the anion with the metal having at least one oxygen atom,thereby generating a metal salt wherein the molar ratio of the totalmetal to the anion (metal:anion) is in the range of 1:4 to 1:120. Thismolar ratio which is not the stoichometric ratio, highly influence theanti corrosive properties of the produced anti-corrosive pigment as willbe shown herein below.

[0059] In one embodiment a phosphoric acid is diluted by water so 5 to15% (wt) solution of phosphoric acid is obtained. A mixing step isperformed by gradually admixing 7 to 35% (wt) magnesium oxide ormagnesium hydroxide to the phosphoric acid solution, so a dispersion ofmagnesium phosphate is obtained. The mixing step may be performed by anyother mixing procedure suitable for obtaining a dispersion of magnesiumphosphate. The obtained dispersion is than dried to yield the anticorrosive pigment The anti corrosive pigment may have a molar ratio ofthe total magnesium to the phosphate in the range of 1:4 to 1:120. Theanti corrosive pigment is than added to waterborne, emulsion, orsolvent-base material and, for example, painted or coated on the surfaceof a metal such as, for example, iron, aluminum, etc.

[0060] In another embodiment of the invention additional magnesiumphosphate salt is gradually admix to the dispersion of the phosphoricacid and magnesium hydroxide or magnesium oxide to yield a molar ratioof the total magnesium to the phosphate in the range of 1:4 to 1:120.

[0061] According to some embodiments of the invention a method forproducing anti-corrosive pigment includes the step of admixing 5 to 15%(wt) phosphoric acid with 7 to 35% (wt) magnesium oxide or magnesiumhydroxide. The admixing is performed so as to obtain pH of about 7 to 11in the solution of the anti corrosive pigment. The anti corrosivepigment thus produced comprising magnesium phosphate with an excess ofmagnesium oxide or magnesium hydroxide. The obtained molar ratio of themagnesium to the phosphate in the pigment is in the range of 1:4 to1:120.

[0062] In some embodiment a method for producing anti-corrosive pigmentincludes the step of gradually admixing 7 to 35% (wt) magnesium oxide ormagnesium hydroxide to 5-15% (wt) phosphoric acid solution so as toachieve solubility of the pigment magnesium-containing ingredients whichis higher than 0.2%.

[0063] In some embodiment a method for producing anti-corrosive pigmentincludes the step of gradually admixing 7 to 35% (wt) magnesium oxide ormagnesium hydroxide to 5-15% (wt) phosphoric acid solution so as toachieve solubility of the pigment magnesium-containing ingredients whichis approximately in the range 0.2%-0.8%.

[0064] In some embodiment a method for producing anti-corrosive pigmentincludes admixing 7 to 35% (wt) magnesium oxide or magnesium hydroxideto a 5-15% (wt) phosphoric acid solution, where part of the magnesiumoxide or magnesium hydroxide is substituted by calcium containingsubstances.

[0065] In some embodiment a method for producing anti-corrosive pigmentincludes admixing 7 to 35% (wt) magnesium oxide or magnesium hydroxideto a 5-15% (wt) phosphoric acid solution, where part of the magnesiumoxide or magnesium hydroxide is substituted by iron containingsubstances.

[0066] In some embodiment a method for producing anti-corrosive pigmentincludes gradually admixing 5-15 (wt) phosphoric acid solution, 3-10%(wt) of at least one amine containing substance and 7 to 35% (wt)magnesium oxide or magnesium hydroxide in water.

[0067] In some embodiment a method for producing anti-corrosive pigmentincludes gradually admixing 3-10% (wt) of at least one amine containingsubstance in water. Admixing phosphoric acid to the amine containingsolution so as 5-15 (wt) of amino phosphoric acid solution is obtained.Gradually admixing 7 to 35% (wt) magnesium oxide or magnesium hydroxideto the amino phosphate solution so as a mixture including magnesiumphosphate, magnesium oxide, and/or magnesium amino phosphate isobtained.

[0068] In some embodiment a method for producing anti-corrosive pigmentincludes gradually admixing 5-15% (wt) phosphoric acid solution, 3-10%(wt) of a base and 7 to 35% (wt) magnesium oxide or magnesium hydroxidein water.

[0069] In some embodiment a method for producing anti-corrosive pigmentincludes gradually admixing 5-15% (wt) phosphoric acid solution, 3-10%(wt) of a combination of at least one amine containing substance and abase and 7 to 35% (wt) magnesium oxide or magnesium hydroxide in water.

[0070] In some embodiment a method for producing anti-corrosive pigmentfurther include admixing of preservatives in a range approximatelybetween 0.1-10% (wt).

[0071] In some embodiment a method for producing anti-corrosive pigmentfurther include admixing of surface active agent in a rangeapproximately between 0.2-2% (wt).

[0072] In some embodiment a method for producing anti-corrosive pigmentfurther include admixing of coloring agent in a range approximatelybetween 0.1-40% (wt).

[0073] Reference is now made to FIG. 1, presents the molar ratio ofMg⁺²/phosphate as a function of the number of equilibrating steps of atri-magnesium diphosphate octahydrate, commercial available product(Fluka, Gemany), which was equilibriate 10 times with fresh aqueousphase. As shown in the small graph the magnesium to phosphate molarratio in this product is about 3:2. This ratio is the stochiometricalratio calculated for the product. This product was found to be ananti-corrosive pigment of low efficiency according to ASTM 53209 andASTM 53210.

[0074] Reference is now made to FIG. 2, presents the molar ratio ofMg⁺²/phosphate as a function of the number of equilibrating steps, of apigment including magnesium phosphate salt in access of 50% magnesiumoxide. The equilibration was conducted up to 10 times with fresh aqueousphase. The molar ratio of Mg⁺²/phosphate in equilibrium after the firstequilibrium step was above 100 and reduced after the 10th equilibriumstep to approximately 18. A steady state was achieved after equilibriumstep 5 meaning that the molar ratio of Mg⁺²/phosphate remainsapproximately steady in the following equilibrium steps. The molar ratioof Mg⁺²/phosphate at steady state is about 1:18 meaning that for eachmolecule of Mg⁺² there are 18 molecules of phosphate. This ratio isdifferent from the stoichometric ratio obtained for the commercialavailable product described in FIG. 1. This pigment was found to be anexcellent anti-corrosive pigment, according to ASTM 53209 and ASTM53210, for aluminum and aluminum containing materials and other metals.

[0075] Reference is now made to FIG. 3, presents the Mg⁺²/phosphatemolar ratio as a function of the number of equilibrating steps, for apigment including magnesium phosphate salt in access of 50% magnesiumoxide and with addition of a pH-buffering agent. The buffering agentthat was added is a water-immiscible aliphatic amine base which iscapable to maintain the pH of the suspension at about pH=10. Theequilibration was conducted up to 10 times with fresh aqueous phase. Themagnesium to phosphate molar ratio at steady state was about 1:18. Thispigment was found to be an excellent anti-corrosive pigment, accordingto ASTM 53209 and ASTM 53210, for iron, iron containing materials andother metallic products.

[0076] The following examples further illustrate and describe theinvention disclosed herein. The invention is not to be limited in scopeby the following examples.

[0077] In all the examples the test was conducted according to ASTM53209 and ASTM 53210 and the results are presented according to thescale introduced in the above mentioned ASTM standards.

EXAMPLE 1

[0078] Phosphoric acid (0.48 Kg of total weight, Agriculture Grade, 85%)was diluted in 3.83 liter of water in ambient temperature and mixed forabout 5 minutes. Magnesium oxide (0.69 Kg, KP Grade by Periclase ltdIsrael), and oleic acid (4 gr) were gradually admixed to the watersuspension in few intervals. The completion of the admixing step wasprovided wherein the pH of the equilibrated pigment product was 10.8. Inis acknowledged that said admixing step was followed with noticeabletemperature changes and thus wherein the temperature decreasing wasrecorded, and wherein the pH titration was performed as described above,the mechanical mixing was terminated, and the suspension was dried in anoven (2.5 hours, above 105° C.).

[0079] The anti-corrosive pigment hereto obtained was incorporated (7%by weight) in a solvent base paint comprising short-alkyd. The paint wasapplied (40 μM) on top of the two sides of iron-made standard Q-panel.One painted and dried side of each panels were subject of standard Xscribe. Triplets of panels were kept in a salt immersion camera (NaCl,5% wt) at ambient temperature. The immersion test results were obtainedby experienced an aided eye after 500 hours, evaluating the generalappearance, scribe, blisters size and degree of each triplet. Theaverage test results of those coated iron to panels were good (accordingto ASTM standard). The results were better than the results obtained forother iron panels coated with similar paints comprising commercialavailable anti-corrosive pigments.

EXAMPLE 2

[0080] Phosphoric acid (0.48 Kg of total weight), Magnesium oxide (0.69Kg), and oleic acid (4 gr) were gradually added to 3.83 liter of waterat ambient temperature, and efficiently admixed. After the mechanicalmixing was terminated, the white suspension was dried by means of aspray drier. The immersion test results were obtained by experienced anaided eye after 500 hours, evaluating the general appearance, scribe,blisters size and degree of each triplet. The average test results ofthose panels were good (according to ASTM standard). The results werebetter than the results obtained for other panels coated with similarpaints comprising commercial available anti-corrosive pigments.

EXAMPLE 3

[0081] A dose of 1.81 Kg of 2,4,6-triamino-s-triazine (C.P. Grade) wasmixed with 30.7 liter water at 16° C. in a 60 liter planetary reactorfor about 5 minutes. Phosphoric acid (3.05 Kg, Agriculture Grade, 98%)was added and mixed for additional 5 minutes. Magnesium Oxide (4.37 Kg,KP Grade by Periclase ltd Israel), oleic acid (2.4 gr) were similarlyadded to the water suspension by few intervals and efficiently admixed.After the mechanical mixing was terminated, the yielded white suspensionwas dried by means of a paddle drier. The solubility of the obtainedproduct in water was in the range of 0.30-0.35% (wt). The immersion testresults were obtained by experienced an aided eye after 500 hours,evaluating the general appearance, scribe, blisters size and degree ofeach triplet. The average test results of those panels were good(according to ASTM standard). The results were better than the resultsobtained for other panels coated with similar pants comprisingcommercial available anti-corrosive pigments.

EXAMPLE 4

[0082] A dose of 1.84 Kg of 2,4,6-triamino-s-triazine (C.P. Grade) wasmixed with 17.6 liter water at room temperature in a 60 liter planetaryreactor for about 5 minutes. Phosphoric acid (3.05 Kg, 85%) was addedand mixed for additional 7 minutes. Magnesium oxide (1.21 Kg), oleicacid (3 gr) and calcium carbonate (6.08 Kg C.P. Grade) were similarlyadded to the water suspension by few intervals and efficiently admixed.After the mechanical admixing was terminated, the white suspension wasdried by means of a screw drier. The solubility of the obtained productin water was in the range of 0.30-0.40% (wt). The immersion test resultswere obtained by experienced an aided eye after 500 hours, evaluatingthe general appearance, scribe, blisters size and degree of eachtriplet. The average test results of those panels were good (accordingto ASTM standard). The results were better than the results obtained forother panels coated with similar paints comprising commercial availableanti-corrosive pigments.

EXAMPLE 5

[0083] Phosphoric acid (3.92 Kg) was added to 9.43 liter of water at17.5° C. and mixed for 2 minutes. Ferrous silicate (15.1 Kg, C.P.Grade), oleic acid (3.8 gr) and magnesium oxide (1.5 Kg) were similarlyadded to the water suspension by few intervals and efficiently admixed.After the mechanical mixing was terminated, the obtained whitesuspension was dried by means of an oven (2.5 hours, above 125° C.). Thesolubility of the obtained product in water was in the range of0.35-0.45% (wt). The immersion test results were obtained by experiencedan aided eye after 500 hours, evaluating the general appearance, scribe,blisters size and degree of each triplet The average test results ofthose panels were good (according to ASTM standard). The results werebetter than the results obtained for other panels coated with similarpaints comprising commercial available anti-corrosive pigments.

EXAMPLE 6

[0084] A dose of 1.81 Kg of 2,4,6-triamio-s-triazine (C.P. Grade) wasmixed with 25.64 liter water at ambient temperature in a 60 literplanetary reactor for about 5 minutes, Phosphoric acid (3.05 Kg) wasadded and mixed for additional 12 minutes. Magnesium hydroxide (9.43 Kg,by Periclase ltd Lsrael), oleic acid (2.4 gr) were similarly added tothe water suspension by few intervals and efficiently admixed. After themechanical mixing was terminated, the produced white suspension wasdried in an oven (2.5 hours, above 145° C.). The immersion test resultswere obtained by experienced an aided eye after 500 hours, evaluatingthe general appearance, scribe, blisters size and degree of eachtriplet. The average test results of those panels were excellent(according to ASTM standard). The results were better than the resultsobtained for other panels coated with similar paints comprisingcommercial available anticorrosive pigments.

EXAMPLE 7

[0085] A dose of dry 13.7 g of tri-magnesium diphosphate octahydrate (byFluka, Germany) was mixed and milled with a dry powder of magnesiumoxide (6.3 g). The immersion test results were obtained by experiencedan aided eye after 500 hours, evaluating the general appearance, scribe,blisters size and degree of each triplet. The average test results ofthose panels were low (according to ASTM standard).

EXAMPLE 8

[0086] A dose of dry 13.7 g of tri-magnesium diphosphate octahydrate (byFluka, Germany) was mixed and magnesium oxide (6.3 g) in 200 ml water.The immersion test results were obtained by experienced an aided eyeafter 500 hours, evaluating the general appearance, scribe, blisterssize and degree of each triplet. The results were better than theresults obtained in experiment 7.

EXAMPLE 9

[0087] A dose of dry 6.3 g of tri-magnesium diphosphate octahydrate (byFluka, Germany) was mixed and milled with a dry powder of magnesiumoxide (13.7 g). The immersion test results were obtained by experiencedan aided eye after 500 hours, evaluating the general appearance, scribe,blisters size and degree of each triplet. The results were better thanthe results obtained for experiment 8.

EXAMPLE 10

[0088] Tri-magnesium diphosphate octahydrate salt (by Fluka, Germany),10 g was equilibrated with 100 ml deionized water for approximately 30min by means of magnetic stirrer (about 300 rpm) at ambient temperature.

[0089] The molar ratio of the total magnesium cations to the totalphosphate anions in an equilibrated aqueous phase is presented inFIG. 1. The X axis of said figure relates to the number of saidequilibrating step, wherein 10 g of the tested tri-magnesium diphosphateoctahydrate salt is equilibrated for approximately 30 min. by means ofmagnetic stirrer with 100 ml water at ambient temperature of about 23°C. The immersion test results were obtained by experienced an aided eyeafter 500 hours, evaluating the general appearance, scribe, blisterssize and degree of each triplet. The average test results of thosepanels were low to moderate (according to ASTM standard).

EXAMPLE 11

[0090] Agricultural grade phosphoric acid (98%) was diluted in water soabout 10% (wt) solution of said phosphoric acid was provided. Thesolution was mechanically mixed with access of magnesium oxide (MagnesiaKP, by Periclas, Israel) in six intervals, so a dispersion comprisinginteralia magnesium phosphate salts, and magnesium oxide was provided.The pH of the obtained dispersion was 9.8. The magnesium cation to thephosphate molar ratio as function of the number of the washing steps isdescribed in FIG. 2. The product was incorporated in paint and tested inan immersion test as defined above. The average test results of thosepanels were excellent (according to ASTM standard). The results werebetter than the results obtained for other panels coated with similarpaints comprising commercial available anti-corrosive pigments.

EXAMPLE 12

[0091] Agricultural grade phosphoric acid (98%) was diluted in water soabout 10% (wt) solution of said phosphoric acid was provided Thesolution was mechanically mixed with melamine so about 10% (wt) melaminephosphate solution was provided. Then, about 30% (wt) magnesium oxidewas admixed in six intervals, so a dispersion analyzed (i.e., by meansof XRD and HRSEM and EDS) to comprise interalia magnesium phosphatesalts, melamine phosphate, melamine magnesium phosphate and magnesiumoxide was provided. The pH of the obtained dispersion was 9.8. Themagnesium cation to the phosphate molar ratio as function of the numberof the washing steps is described in FIG. 3. The product wasincorporated in paint and tested in an immersion test as defined above.The average test results in aluminum panels and other metal ware panelswere excellent (according to ASTM standard). The results were betterthan the results obtained for other panels coated with similar paintscomprising commercial available anti-corrosive pigments.

What is claimed is:
 1. An anti-corrosive pigment comprising a metal saltcomprising a metal cation and an anion; and a metal having at least oneoxygen atom; wherein the molar ratio of the total metal to said anion isin the range of 1:4 to 1:120.
 2. The pigment of claim 1, wherein saidmetal is magnesium, calcium or iron, or any combination thereof.
 3. Thepigment of claim 1, wherein said metal is magnesium.
 4. The pigment ofclaim 1, wherein said metal having at least one oxygen atom is magnesiumhaving at least one oxygen atom selected from magnesium oxide, magnesiumhydroxide or any combination thereof.
 5. The pigment of claim 1, whereinsaid metal is iron.
 6. The pigment of claim 1, wherein said metal havingat least one oxygen atom comprising iron and selected from ferrousoxide, ferrous silicate, a slag material, an iron containing industrialeffluent, or any combination thereof.
 7. The pigment of claim 1, whereinsaid metal is calcium.
 8. The pigment of claim 1, wherein said metalhaving at least one oxygen atom comprising calcium and selected fromcalcium oxide, calcium hydroxide, calcium bicarbonate, calciumcarbonate, or any combination thereof.
 9. The pigment of claim 1,wherein said metal salt is a phosphate salt.
 10. The pigment of claim 1,wherein said metal salt is magnesium phosphate.
 11. The pigment of claim1, further comprising a pH buffering agent.
 12. The pigment of claim 11,wherein said pH buffering agent is an amine-containing substance. 13.The pigment of claim 12, wherein said pH buffering agent is anamine-containing substance selected from monoethyl amine, diethyl amine,triethyl amine, monoethanol amine, diethanol amine, triethanol amine,1,2-diazide, 1,2,3-triazide, dicyclohexylamine, aliphatic amines,aromatic amines, melamine, hexamethylentetramine andpentaethylenetetramine, ammonium hydroxide, amino acid, and poly amines.14. The pigment of claim 11 wherein said pH buffering agent is a base.15. The pigment of claim 14 wherein said base selected from potassiumhydroxide, sodium hydroxide, calcium hydroxide.
 16. The pigment of claim1, wherein the final pH of said pigment is about 7 to
 11. 17. Thepigment of claim 1, wherein the solubility of said pigment inequilibrated water is greater than about 0.2%.
 18. The pigment of claim1, wherein the solubility of said pigment in equilibrated water is about0.2-0.8%.
 19. The pigment of claim 1, wherein said metal having at leastone oxygen atom comprises magnesium compound in combination with acalcium compound.
 20. The pigment of claim 19, wherein said magnesiumcompound selected from magnesium oxide, magnesium hydroxide or anycombination thereof, and wherein said calcium compound selected fromcalcium oxide, calcium hydroxide or any combination thereof.
 21. Thepigment of claim 1, wherein said metal having at least one oxygen atomcomprises magnesium compound in combination with an iron compound. 22.The pigment of claim 21, wherein said magnesium compound is magnesiumoxide, magnesium hydroxide or any combination thereof, and wherein saidiron compound is iron oxide, iron hydroxide or any combination thereof.23. The pigment of claim 22, wherein said iron compound is ferrousoxide, ferrous silicate, a slag material, or an iron containingindustrial effluent.
 24. The pigment of claim 1, wherein said molarratio of said metal to said anion is about is about 1:18 when using saidpigment on aluminum and aluminum containing materials.
 25. The pigmentof claim 1, wherein said molar ratio of said metal to said anion isabout is about 1:18 when using said pigment on iron and iron containingmaterials.
 26. The pigment of claim 1, wherein said molar ratio of saidmetal to said anion is about 1:4 to 1:80.
 27. The pigment of claim 1,wherein said molar ratio of said metal to said anion is about 1:20 to1:50.
 28. The pigment of claim 1, wherein said molar ratio of said metalto said anion is about 1:50 to 1:80.
 29. The pigment of claim 1, whereinsaid molar ratio of said metal to said anion is about 1:80 to 1:100. 30.The pigment of claim 1, wherein said molar ratio of said metal to saidanion is about 1:80 to 1:120.
 31. The pigment of claim 1 furthercomprising a preservative.
 32. The pigment of claim 31 wherein saidpreservative is in a range of 0.1 to 10% (w/w) of the pigment weight.33. The pigment of claim 31 wherein said preservative is selected frombiocides, fungicides, algaecides, sporocides, insecticides, orherbicides.
 34. The pigment of claim 31 wherein said preservative isselected from citrimide, chlorohexadine and the like, and quaternaryamines, such as Querton KKBCL-50 or Querton 246, Querton GCL-50, Querton210CI50, or Querton GCL-50.
 35. The pigment of claim 31 wherein saidpreservative is an inorganic preservative selected from boric acid,sodium borate, zinc oxide or cupper oxide.
 36. The pigment of claim 1further comprising a surface-active agent.
 37. The pigment of claim 36wherein said surface active agent is in the range of 0.2 to 2% (w/w) ofthe pigment weight.
 38. The pigment of claim 36 wherein said surfaceactive agent is lingosulphonates or oleic acids.
 39. The pigment ofclaim 1 further comprising a coloring agent.
 40. The pigment of claim 39wherein said coloring agent is in the range of 0.1 to 40% (w/w) of thepigment weight.
 41. The pigment of claim 39 wherein said coloring agentis selected from fuchsin, rohdamine, methylene blue, iron oxide, methylviolet, or alizarine.
 42. The pigment of claim 1 further comprising a UVstabilizer.
 43. The pigment of claim 1 further comprising a UV absorber.44. The pigment of claim 1 further comprising a UV enhancer.
 45. Use ofthe pigment of claim 1 in a waterborne material selected from paint,coating, plaster or filler wherein said pigment is in the range of 1.7to 25% (w/w) of said waterborne material.
 46. Use of the pigment ofclaim 1 in a solvent base material selected from paint, coating, plasteror filler wherein said pigment is in the range of 1.7 to 25% (w/w) ofsaid solvent base material.
 47. Use of the pigment of claim 1 in anemulsion wherein said pigment is in the range of 1.7 to 25% (w/w) ofsaid emulsion.
 48. A method for the production of an anti-corrosivepigment said pigment comprising a) a metal salt comprising a metalcation and an anion, and b) a metal having at least one oxygen atom;said method comprising the step of mixing an acid of said anion withsaid metal having at least one oxygen atom, thereby generating saidmetal salt, wherein the molar ratio of the total metal to said anion isin the range of 1:4 to 1.120.
 49. The method of claim 48 wherein saidacid is phosphoric acid and said metal having at least one oxygen atomis magnesium oxide or magnesium hydroxide.
 50. The method of claim 49wherein said acid is diluted by water to obtain a 5-15% (wt) solution.51. The method of claim 49 wherein said metal having at least one oxygenatom is gradually added to a range of 7-35% (wt) of the pigment.
 52. Themethod of claim 49 wherein additional magnesium phosphate salt isgradually admix to said phosphoric acid and metal having at least oneoxygen atom to yield a molar ratio of the total magnesium to thephosphate in the range of 1:4 to 1:120.
 53. The method of claim 48comprising the step of admixing 5 to 15% (wt) phosphoric acid with 7 to35% (wt) magnesium oxide or magnesium hydroxide so as to obtain pH ofabout 7 to 11 in said anti corrosive pigment.
 54. The method of claim 48comprising the step of gradually admixing 7 to 35% (wt) magnesium oxideor magnesium hydroxide to 5-15% (wt) phosphoric acid solution so as toachieve solubility of the pigment magnesium-containing ingredients whichis higher than 0.2%.
 55. The method of claim 48 comprising the step ofgradually admixing 7 to 35% (wt) magnesium oxide or magnesium hydroxideto 5-15% (wt) phosphoric acid solution so as to achieve solubility ofthe pigment magnesium-containing ingredients which is approximately inthe range 0.2%-0.8%.
 56. The method of claim 48 wherein said metalhaving at least one oxygen atom comprising magnesium oxide, magnesiumhydroxide and calcium containing substances.
 57. The method of claim 48wherein said metal having at least one oxygen atom comprising magnesiumoxide, magnesium hydroxide and iron containing substances.
 58. Themethod of claim 48 comprising the step of gradually admixing 5-15% (wt)phosphoric acid solution, 3-10% (wt) of at least one amine containingsubstance and 7 to 35% (wt) magnesium oxide or magnesium hydroxide inwater.
 59. The method of claim 48 comprising the steps of admixing 3-10%(wt) of at least one amine containing substance in water; admixingphosphoric acid to said amine containing solution so as 5-15% (wt) ofamino phosphoric acid solution is obtained. admixing 7 to 35% (wt)magnesium oxide or magnesium hydroxide to the amino phosphate solutionso as a mixture comprising magnesium phosphate, magnesium oxide, ormagnesium amino phosphate is obtained.
 60. The method of claim 48comprising the step of gradually admixing 5-15% (wt) phosphoric acidsolution, 3-10% (wt) of a base and 7 to 35% (wt) magnesium oxide ormagnesium hydroxide in water.
 61. The method of claim 48 comprising thestep of gradually admixing 5-15% (wt) phosphoric acid solution, 3-10%(wt) of a combination of at least one amine containing substance and abase and 7 to 35% (wt) magnesium oxide or magnesium hydroxide in water.62. The method of claim 48 further comprising the step of admixing apreservative.
 63. The method of claim 62 wherein said preservative is ina range of approximately 0.1-10% (wt).
 64. The method of claim 48further comprising the step of admixing a surface active agent.
 65. Themethod of claim 64 wherein said surface active agent is in a range ofapproximately 0.2-2% (wt).
 66. The method of claim 48 further comprisingthe step of admixing a coloring agent.
 67. The method of claim 66wherein said coloring agent is in a range of approximately 0.1-40% (wt).